11:00
$(\mathbb{C};+,\cdot,CM)$
Abstract
In this ``journal club''-style advanced class, I will present some material from a recent paper of Tom Scanlon https://arxiv.org/abs/2508.17485 . Motivated by the question of decidability of the field C(t) of complex rational functions in one variable, he considers the structure $(\mathbb{C};+,\cdot,CM)$ of the complex field expanded by a predicate for the set CM of j-invariants of elliptic curves with complex multiplication (the "special points"). Analogous to Zilber's result from the 90s on stability of the expansion by a predicate for the roots of unity, Scanlon shows that Pila's solution to the André-Oort conjecture implies that this structure is stable, and moreover that effectivity in this conjecture due to Binyamini implies decidability. I aim to explain Scanlon's proof of this result in some detail.